This invention relates to a heat jacket being placed on the chimney flue and passing air through the passageway provided therebetween for redistribution to areas bein heated. More specifically, however, this invention is concerned with providing to the areas to be heated air drawn in from the outside which is fresh and humid which is heated by the heat given off from the furnace flue pipe extending from the furnace to the top of the building. Utilization of heat produced by a flue pipe is disclosed in patents such as U.S. Pat. Nos. 2,890,866 and 3,124,197, however, these patents teach reheating used air rather than drawing in fresh humid air and heating it for distribution to the areas to be heated.